The present invention relates to an ultrasonic diagnostic apparatus for transmitting ultrasonic waves to a tissue in a living body, detecting the phases of ultrasonic echo signals reflected from the living body by using phase detecting means to calculate tissue movement or blood flow velocity in the living body according to the detected phases, and displaying the calculated result.
A conventional ultrasonic diagnostic apparatus has various functions, such as a B-mode function for displaying tomographic images of a tissue in a living body, an M-mode function for displaying a temporal variation of the movement of a tissue in a living body, an FFT Doppler mode function for displaying a temporal variation of blood flow velocity, and a color Doppler mode function for displaying the moving state of a moving region in a living body, such as blood flow, by coloring the moving region according to its moving direction.
In those instances where such a conventional ultrasonic diagnostic apparatus is used to diagnose carotid arteries for the purpose of an arteriosclerosis diagnosis, the characteristic of a lesion is determined by using the B-mode function to evaluate the inner diameter of a blood vessel and the thickness of the blood vessel wall; using brightness in a tomographic image from the B-mode imaging to evaluate a raised lesion resulting from thrombus adhesively accumulated on the blood vessel wall; using the M-mode function to evaluate the temporal variation of the inner diameter of the blood vessel in response to a heartbeat; and using the FFT Doppler function or the color Doppler function to evaluate the blood flow velocity in the stenotic region of the blood vessel due to the raised lesion.
Further, Japanese Patent Laid-Open Publication No. Hei 9-323485 discloses a Tissue Doppler Imaging technique to measure the movement of a tissue in a living body. This technique is directed to grasp the movement of a tissue in a living body quantitatively by imaging a target region with color according to the magnitude and/or direction of the tissue movement.
When diagnosing carotid arteries for the purpose of the arteriosclerosis diagnosis, it is necessary to grasp easily the relationship between blood flow variation and arterial wall movement in order to evaluate an influence of a raised lesion arising in the carotid arteries.
However, when the aforementioned conventional ultrasonic diagnostic apparatus is used to diagnose a raised lesion mainly arising from thrombus, the obtained tomographic image of the raised lesion is displayed with low brightness due to properties of the tissue of the raised lesion. Thus, in the evaluation method using the B-mode function, there is a problem that it is difficult to discover such a lesion, and it is impossible to quantitatively evaluate the characteristic of the lesion according to brightness in the obtained tomographic image.
In the conventional ultrasonic diagnostic apparatus additionally employing the color Doppler function, even if a lesion has a low brightness which is difficult to discover through the B-mode function, the lesion can be colored to distinguish it from lumen having a blood flowing therethrough, thereby providing higher diagnostic accuracy than that obtained by using only the B-mode function. However, it is difficult to quantitatively grasp the arterial wall movement in relation to the blood pressure and/or blood flow variation.
In addition, for achieving the color Doppler function, it is essential to perform a given processing for accurately distinguishing blood flow (fast movement) from body movement (slow movement) to pick up information related only to the blood flow. As a result, signals representing the amount of the slow movement from the living body are filtered out, and thereby the tissue movement and blood flow variation in the living body cannot be measured simultaneously.
Even though the quantitative ascertainment of the tissue movement can be achieved by additionally employing the tissue Doppler imaging, it is still difficult to ascertain the arterial wall movement in relation to the blood pressure and/or blood flow variation.
The present invention is directed to solve the aforementioned problems in the conventional apparatus. It is, therefore, an object of the present invention to provide an improved ultrasonic diagnostic apparatus capable of simultaneously measuring the movement velocity and displacement of a tissue in a living body, such as blood flow or arterial wall, particularly for diagnosing lesions in the circulatory system, so that a display can be obtained in which the relationship between the blood flow variation and the arterial wall movement can be easily obtained.
In order to achieve the above object, the present invention provides an ultrasonic diagnostic apparatus comprising ultrasonic transmitting/receiving means for transmitting ultrasonic pulses into a living body and receiving ultrasonic reflected waves reflected from the living body through an ultrasonic probe; phase detecting means for detecting each phase of the ultrasonic reflected waves received by the ultrasonic transmitting/receiving means; phase-difference detecting means for detecting a phase-difference between a plurality of phase signals detected continuously by the phase detecting means; data analyzing means for analyzing a movement of a tissue including a blood flow in the living body according to the detected phase difference; and display means for displaying the movement of the living body tissue. Because of this construction, it is possible to analyze the movement of the living body tissue through a simplified method of detecting the phase-difference between the received ultrasonic signals.
In the above ultrasonic diagnostic apparatus of the present invention, the ultrasonic probe may include a plurality of ultrasonic transducers. In this case, the ultrasonic diagnostic apparatus further includes delay control means for controlling each delay value of the ultrasonic pulses and ultrasonic reflected waves which are transmitted and received by each of the plurality of ultrasonic transducers to control each deflection angle of acoustic lines defined by the ultrasonic pulses and the ultrasonic reflected waves. Further, the phase detecting means is adapted to detect the phase-difference for each of the plurality of acoustic lines having different deflection angles, and the data analyzing means is adapted to calculate the movement velocity and displacement of the living body tissue according to the phase-difference for each of the plurality of acoustic lines. Because of this construction, it is possible to calculate the movement velocity and displacement of the living body tissue with a high degree of accuracy through a simplified method of detecting the phase-difference of ultrasonic received signals for each of the plurality of acoustic lines having different distortion angles.
In the above ultrasonic diagnostic apparatus of the present invention, the data analyzing means may be adapted to detect the orthogonal and parallel components of the movement velocity of the living body tissue according to the phase-difference for each of the plurality of acoustic lines. And the data analyzing means may be adapted to calculate the movement velocity and displacement of the living body tissue according to the detected orthogonal and parallel components of the movement velocity. In this case, the orthogonal and parallel components are orthogonal to and parallel to the surface of the ultrasonic probe, respectively. Because of this construction, it is possible to provide enhanced accuracy in the calculation of the movement velocity and displacement of the living body tissue based on the detection of the phase-difference of ultrasonic received signals.
The ultrasonic diagnostic apparatus according to the present invention may further include transducer selecting means for selecting the plurality of ultrasonic transducers. The transducer selecting means is adapted to form a plurality of ultrasonic transducer sets each composed of a given number of adjacent ultrasonic transducers selected from the plurality of ultrasonic transducers, and to select a plurality of the ultrasonic transducer sets. In this case, the data analyzing means is adapted to calculate the movement velocity and displacement of the living body tissue according to the phase-difference for each of the acoustic lines of the selected ultrasonic transducer sets. Because of this construction, it is possible to deflect the acoustic line easily, and it is possible to detect phases from a plurality of acoustic lines so as to calculate the movement velocity and displacement of the living body tissue accurately.
In the above ultrasonic diagnostic apparatus of the present invention, the delay control means may be adapted to arbitrarily control each deflection angle of the acoustic lines of the ultrasonic transducer sets. In this case, the data analyzing means is adapted to calculate the movement velocity and displacement of the living body tissue according to the phase-difference for each of the acoustic lines. Because of this construction, it is possible to change the deflection angle of the acoustic line easily, so as to provide enhanced flexibility in calculating the movement velocity and displacement of the living body tissue.
The ultrasonic diagnostic apparatus of the present invention may further include diagnostic-image construction means for constructing an ultrasonic diagnostic image according to information related to the ultrasonic reflected waves. The ultrasonic diagnostic image may have a plurality of measurement regions. And at least one of the measurement regions can be selected from the ultrasonic diagnostic image constructed by the diagnostic image construction means. In this case, the phase-difference detecting means is adapted to detect the phase-difference of the ultrasonic reflected waves associated with the at least one of selected measurement region simultaneously or almost simultaneously, so as to allow the data analyzing means to calculate the movement velocity and displacement of the living body tissue in the selected measurement region. Because of this construction, it is possible to calculate the movement velocity and displacement of the target region while checking the target region by the ultrasonic diagnostic image, so that accuracy in diagnosis is improved.
In the above ultrasonic diagnostic apparatus of the present invention, it is possible to select at least one of any measurement region from the ultrasonic diagnostic image constructed by the diagnostic image construction means. The delay control means may be adapted to set each deflection angle of the acoustic lines for each of scan frames, and the phase-difference detecting means is adapted to detect the phase-difference of the ultrasonic reflected waves for each of the scan frames having an arbitrarily-set deflection angle, simultaneously or almost simultaneously, in the at least one of selected measurement regions. Because of this construction, it is possible to calculate the movement velocity and displacement of the target region without degrading the image quality of the ultrasonic diagnostic image.
The ultrasonic diagnostic apparatus of the present invention may further include means for converting the movement velocity and displacement in the living body tissue to polar coordinate system to determine velocity value and angle. Because of this construction, it is possible to provide enhanced accuracy in the calculation of the movement velocity and displacement of the living body tissue.
The ultrasonic diagnostic apparatus of the present invention may further include electrocardiographic-signal input means for inputting a signal from an electrocardiograph, and means for displaying an image on the display means to provide the relationship between the input electrocardiographic signal and the displacement of an arterial wall. Because of this structure, it is possible to simultaneously display the displacement of the living body tissue and the electrocardiographic waveform. Thus, it is particularly effective in a diagnosis of the circulatory system.
In the above ultrasonic diagnostic apparatus of the present invention, the data analyzing means may be adapted to calculate the movement velocity and displacement of each of an arterial wall and an intra-arterial blood flow, and to determine the relationship between the movement velocity or displacement of the arterial wall and the movement velocity or displacement of the intra-arterial blood flow, so as to allow the display means to display a graph representing the relationship. Because of this construction, it is possible to provide the graph representing the relationship between the movement velocity or displacement of the arterial wall and the movement velocity or displacement of the intra-arterial blood flow. Thus, it is possible to ascertain the state of the lesion in the diagnostic region.
Further, in the above ultrasonic diagnostic apparatus of the present invention, the data analyzing means may be adapted to arbitrarily set a delay time from the time when an R-wave of the electrocardiographic signal is generated, and to calculate the movement velocity and displacement of each of an arterial wall and an intra-arterial blood flow at the set delay time, so as to allow the display means to display a graph representing the relationship between the movement velocity or displacement of the arterial wall and the movement velocity or displacement of the intra-arterial blood flow. Because of this construction, it is possible to provide the graph representing the relationship between the movement velocity or displacement of the arterial wall and the movement velocity or displacement of the intra-arterial blood flow in conjunction with a heartbeat. Thus, it is possible to ascertain the relationship between the lesion and the heartbeat.
The ultrasonic diagnostic apparatus of the present invention may further include blood-pressure input means for inputting a signal from a blood-pressure meter. In this case, the data analyzing means is adapted to normalize the displacement of an intra-arterial blood flow with a maximum blood pressure and a minimum blood pressure entered from the blood-pressure meter to convert the displacement into a blood pressure variation so as to allow the display means to display a graph representing the relationship between the movement velocity or displacement of the arterial wall and the blood pressure variation. Because of this construction, it is possible to provide the graph representing the relationship between the movement velocity or displacement of the arterial wall and the blood pressure variation so as to ascertain the relationship between the blood pressure variation and the arterial wall.